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Mounting a box plow on an articulated truck

I'm starting this thread since people had asked for details on the construction details on my truck when I had asked a question on the airport forum. It was diverging from the original question, and I thought it would be better to have a thread on the construction itself.

I am an engineer, and will probably ping the geek meter, but feel free to ask questions and I will do my best to answer them.

Since every design has a reason, some explanation is in order. Feel free to skip.

The mission is to plow the ramp areas among some hangar buildings.

I have been involved in the construction of new hangars at the Zelienople Municipal Airport. This involved the construction of a new ramp area and some buildings, as shown in the attached image.

The airport has some conventional highway plow trucks, two pickups with plows, and a forestry machine with a 16' broom. However, with the new hangar construction, the plow trucks won't work because there are buildings on both sides of the taxilanes.

The narrower taxilanes are 75 feet wide, and the larger is 90 feet. The taxilanes are 700 feet long, and there is a 20 foot road between the hangar buildings and the detention pond.

I had a truck (1991 Moxy 6225B) that I had purchased for moving dirt during hangar construction. I was contemplating the purchase of a loader to use as a prime mover, when I realized that the truck had similar specifications except for stacking. The truck has articulated steering (important with a big box plow), and 260 hp. It weighs about 33,000 lb empty and up to 90,000 lb if I fill the bed. This is comparable to a CAT 966 or 972. One advantage to the truck is that the front wheels and cab can roll left/right independently of the rear wheels, so that there is better following of the pavement.

I wound up choosing a 16 foot wide Super Duty from Protech.

The reason for the choice of a Super Duty rather than a standard loader model was that a Super Duty (or Giant from Avalanche, or other equivalent) doesn't spill as much on the long pushes, due to a 5x7 sideplate instead of a 4x4.

Since the taxilanes/ramp area are not driven on prior to being plowed, packed snow/ice is generally not encountered. Additionally, there are no curbs, protruding manholes, etc. to hit, and no trip edge is required. Thus, a rubber edge is likely preferable to a steel edge for this application.

I wanted the plow to fit between the hangars and detention pond, which limited the width, especially when trying to turn around the corner.

An important criterion was that the the truck not get stopped no matter how deep the snow. Spilling was OK, stopping was not. A smaller plow allows a higher concentration of force.

Since the drainage for the hangar rows had swales with grates in the middle, the left and right of the taxilanes get plowed separately to avoid leaving snow due to spanning the low line in the middle of the taxiway.

For the 75' taxilanes, this gives 37.5 feet, and it would take 3 pushes per side with any pusher less than 20 feet. For the 90 foot taxilane, it would take 3 pushes per side for any pusher less than 24 feet.

The longer the blade, the less well it can follow irregularities in the pavement, and it will tend to leave more snow underneath. Since no salt is allowed on airports, getting a clean push is important.

Sitting in the cab and using stakes to approximate the sides, I felt that larger than 20' was too wide to keep an eye on when operating within a few feet of buildings.

If I was doing this build for a wide-open lot (stadium, etc.) I would probably go with a 20'-24'.

Something to keep in mind is that the 16' Super Duty weighs 4300 lb, and the 20' 5400 lb. This weight gets moved sideways whenever the truck turns, either sliding on the pavement or in the air. This weight is 15' or so in front of the pivot, and so the support structure needs to be engineered for these sideloads.

Attached is a picture of what is left after a single pass. I don't know if it is better or worse than other plows. It melts away reasonably quickly if the sun is out. If the sun isn't we can broom it to get all the way to asphalt.

Although the calculations indicate it should spill before the end with more than 1" of snow, I have found it takes about 2" before it spills. I will make some precise measurements next season, since it seems like we are done for the year in western PA.

Also subscribing...
I am surprised by the choise of rubber edge for that distance of carry but it seems to work well.
I wanted to be an engineer when I was younger cause I loved the striped hat and tooting the horn...

I chose the rubber edge after discussions with both Avalanche and Protech. I didn't talk to other manufacturers, since I couldn't find any other one making the large (height and depth, not width) pushers. I don't know how it compares to a sectional, or if sectionals leave small trails between segments. No sectionals that I am aware of are built with such large sideplates.

At a small airport, when it is snowing, none of the small airplanes are flying, and so you don't get anyone driving (or even much walking) on the snow prior to it being plowed. The runways, taxiways, and commercial ramp are kept clear by conventional plows.

As a result, hardpack isn't an issue. A rubber edge conforms better to small pavement irregularities than a steel edge.

Also, you know for a fact that there is nothing under the snow. The ramps are regularly checked for FOD (Foreign Objects) so even screws, bolts, etc. aren't on the ramp, so a trip edge isn't necessary. The one concern is if you somehow hooked on the drainage gratings.

Lastly, the FAA specs for the asphalt are different from normal DOT specs, with a lot more sand in the mix and different aggregate. Paving frequency is once every 20 years or so. I didn't want to run the risk of tearing up the pavement.

I don't know how this pusher (it weights 4300 lb) and a rubber edge would work where vehicles had driven. It might require a different pusher. I'll try it out on the parking lots next to the hangars next year and report back.

I think it will also be interesting to see how it continues to clean as the rubber edge wears, and how often re-adjustment is needed.

The box plow had to be able to be lifted so it wouldn't drag during transport or while backing up.

The mount had to allow the left and right sides of the plow to float independently to allow "drop and go" operation and optimum squeegee efficiency.

The mount had to be designed for at least 50,000 lb of push.

The reactions to the plow force shouldn't add lift or downforce to the box plow.

To attach, I had two frame rails that are used to support the engine. On this truck, they are 4x10 rectangular tubes, with the inside about 32 inches apart.

Originally, I had designed a weldment that would attach to the frame rails at the back and the tow hook at the front to provide a mounting surface flush with the front of the truck, with the bottom at the height of the pushing beam of the plow. A 4-bar linkage would extend forward from that so that there would be no up or down force resulting from the pushing, and a single hydraulic cylinder using another bar would perform the lifting. A picture is attached.

Ultimately, I dropped this configuration, since to provide the resistance to side force and still have the ability to float the sides independently, I needed some x-bracing both in the 4-bar and in the part under the truck, but this needed to not interfere with the floating. The more I worked, the more complex it became.

It also put the back of the plow 4 feet or so in front of the truck, which would add to the side loads.

Attached Files:

Having abandoned the 4-bar, I took inspiration from tractor 3-point hitch linkages. I added two inside tubes to increase the allowable push force for a given bar weight. and increase the resistance to the side force.

Top, side, and oblique views are attached. The yellow represents the back of the box plow, and the orange the push beam, the grey and black the frame rails and tow hooks. Green is hollow tubes.

I used Cat 3 3-point hitch repair ends at the ends of the tubes. Since all 4 float, and the centers on the truck and on the push beam are all in respective lines, the plow can move the left up and down independently of the right, and tilt freely to follow the contours of the asphalt.

I used 8 pieces of 1/2 thick angle and had it plasma cut, including the holes. I had had good luck in the past with plasma cutting of holes in 1/4 inch material that were so good they looked like they were milled. It didn't work so well at 1/2 inch, and I had to ream the holes. I think if I did it over, I would have the holes put in by a machine shop.

One unfortunate thing about the CAT 3 ends is that the hole is 1 7/16 diameter, which is not a common bolt size. For pins, I used drill rod which I cut on a bandsaw and shaft collars. After welding the angles onto the push beam, using the drill rod for alignment while tacking, I re-reamed the holes so that the drill rod turned and moved easily but wasn't sloppy. The drill rod isn't hardened, which was intentional to have a sacrificial part, since a 3' piece is cheap compared to repairing the angles or parts welded to the truck.

The rear support on the truck is comprised of a short piece of 6x6 boxbeam, with angle welded to it to support the piece sticking our from the frame rail. The piece was as long as I could get given other parts (engine and cab mounts, suspension parts) welded to the frame rail to minimize stresses on the weld. I should mention that on the truck I had, welding on the frame rails was permitted and there was a procedure in the maintenance manual for doing so. A 6x6 H-beam (non-tapered flanges) was welded to the bottom of the box beam, and had a hole put in the web for the pins. 1" thick plates with holes for the pins were welded into the open sides of the H-beam, forming individual pockets for the push tubes. Reaming was a pain, and I would probably weld the plates in and then pay a machine shop to bore the holes if I did it again.

The reason for using the 6x6 box as a standoff rather than just welding the H-beam to the frame rail was twofold. One was that the beams had less of an angle when pushing, minimizing (but not eliminating) downforce. The second was that by doing so I could gain more height when lifting the box, as shown in the side view It is still not much (just over a foot) but it is adequate for what I need.

On the front of the truck, I used a 1/2 thick plate with various angles and parts welded on to make a mount for lifting the plow hydraulically and restraining the front from rotating too far when I lifted it. I used four 1" bolts to attach it to the C-channel that formed the front "bumper" of the truck. It looks a little weird because I needed to get the top mounts of the hydraulic cylinders up high enough to lift the plow, and the hood has to be able to open.

Only the outer tubes are used to lift the plow. The angle of the cylinders help both with centering and making sure the plow comes up evenly. I added bars on the top and bottom of the outer tubes so that the front of the truck would be lifted before they would buckle.

The only parts that need to stay attached to the truck are the rear attach points, but they are close to the wheels and shouldn't affect its ability to move dirt. Although I could remove it, I will probably leave the front plate attached when the plow is off, since it isn't in the way.

I have attached some pictures of the actual connection to the plow. My apologies to those who saw these in the other thread. I will have new pictures by Wednesday.

Protech had designed the push beam so it was restrained by pins, so no chains or binders, which makes the connection easy. I attach the tubes to the . One pin went in fine, but the other took some persuasion and still didn't make it all the way in. I'll ream the holes for next year.

When I built everything and it was time to start laying it out, I found that I had forgotten one important detail in the CAD model.....the gussets on the push beam.

After smacking myself upside the head, and kicking myself in the butt, I decided to mount the outside tubes to the outside of the gussets, since that would be better for side loads.

Of course, now the tubes were too short by about 8", so I bought longer ones for the outside.

It also meant that the hydraulic cylinders I had already bought were too short, so that the tubes would hit the frame if I retracted it all the way, and they wouldn't go down far enough to allow the plow to float. The carefully thought out geometry for the lifting plates on the tubes was also wrong, so the tubes are rotated when I lift the plow, rather than the hydraulic force passing through a line connecting the rotational center of the hitch ends.

It doesn't appear to hurt anything, but it's one of those things that pisses me off every time I see it. At any rate, a lesson in humility in case I needed another one.

As the pictures show, I kludged it together with some clevises, etc. so that it worked for this season, but I'll have to make some links or make a different hydraulic mounting plate for next year.

Although I had given the welder precise angles for the hitch ends with respect to the tube inserts (fortunately done after I found out about my gusset mistake), he did not keep them clamped to that angle after tacking and they moved. It works, but they aren't as straight as I would like.

After I got the inserts back, I put 4 of them into the tubes and had them welded there, and put the other 4 in but didn't weld them, then sent everything out for sandblast and paint. The reason for this is that this was I could compensate for inevitable slight differences in placement of the mounts on the truck, the angles on the push beam, tube length, etc.

When everything came back, I put the tubes and pushbeam on the truck. I then whacked the push beam back and forth with a BFH until it was centered and parallel with the front of the truck. Only one chance to get it aligned, so I was pretty careful. The remaining 4 were then welded into that position.

The truck, of course, was not designed with a front mounted plow in mind. This particular truck (and other Moxys until about 2000 or so) had single acting cylinders to lift the bed. Volvos and most others used double acting cylinders.

I wanted to use double acting cylinders to avoid moisture and dirt getting into the cylinder, and because I had to pull with the cylinders given the overall mechanical design I went with.

The Moxy is an open center system, with the steering pump first in line after the main pump and the air over hydraulic dump bed valve behind that. From a safety perspective, the valve had to go after the steering valve. I decided to put the valve for the plow after the valve for the dump bed, since I could then bypass it when the plow wasn't on.

I decided to go with a monoblock loader valve, since that would give me lift and tilt, as well as a float detent. The valve is a 25 gpm valve, which is way more than needed for the plow cylinders, but is required because of the hydraulic pump output, and in an open center system the pump flow output is at its maximum for a given RPM all the time.

I mounted the valve in the engine compartment to the lifting eye for the truck. It is actuated through push/pull cables to a joystick mounted in the cab. In addition to being convenient and allowing straight cable runs, it will help keep the hydraulic fluid between the valve and cylinders warm in the winter. The loader valve and joystick are Prince Hydraulics, and the cylinders (12" stroke, 3"bore, 1.5" rod) I purchased from Surplus Center, so I am not sure who made them.

Even though I am lifting using the rod side, it still give me 12,000 lb of pull force per cylinder, which is more than enough. I would have gone smaller, but with the pump output and an open center system, a smaller cylinder would have resulted in jerking the plow up too quickly.

As the pictures show, I haven't completed the installation. The reason for this is that the dump bed valve, where I need to break into the system, is located behind the left fender. For this winter, I decided to just tap into the dump bed hydraulic output, so I ran a 15' hose from the fitting for the dump cylinders up to the plow cylinders, and just used some coffee filters and a rag zip-tied around a hose to filter the air going into and out of the unconnected side of the cylinders.

The dump valve has two return lines. One is from the dump valve for when the bed is coming down and one is for the fluid just going through the valve. These join together with the return lines from the steering valve and the emergency steering pump (manual steering is not possible) prior to going back to the tank.

Prior to next season, I need to have some custom lines made to go from the second return line to the loader valve, and then tee into the return lines back to the hydraulic tank.

The hydraulic lift cylinders are mounted with the rod down to minimize dirt accumulation. The plate on the front of the truck is 3/4" thick, and has two 1/2 inch spacer plates welded to it, and then two more plates welded to those to give a 1.75 inch space for the ball end of the cylinders to fit into. By doing this symmetrically, the lift force puts the attachment to the front of the truck in shear, and minimizes any bending moment.

The plates are staggered a bit to allow fillet welding on each plate.

There are plates welded to the top and inside of the "ears" to add bending stiffness and strength to the cylinder supports.

The cylinders have ball ends at both ends because as the plow is lifted, the lift point on the arms moves both fore/aft and in/out with respect to the plate.

As may be obvious from the picture, I don't have working headlights at the moment. The truck headlights work, but are stuck behind a 60" moldboard. That hasn't been an issue yet, as I've been able to plow during the day.

I was planning on using the two bars that stick out from the side of the cab. They were for optional recognition lights which my truck doesn't have. Fortunately, with LED technology, I can get some fairly bright floods/spots that will not overload the original wiring to those locations.

Do people have advice on what whether mounting at the top of the cab would be too high? Although the truck would be road legal in Europe, I am not worried about legal height for the road.

As may be obvious from the picture, I don't have working headlights at the moment. The truck headlights work, but are stuck behind a 60" moldboard. That hasn't been an issue yet, as I've been able to plow during the day.

I was planning on using the two bars that stick out from the side of the cab. They were for optional recognition lights which my truck doesn't have. Fortunately, with LED technology, I can get some fairly bright floods/spots that will not overload the original wiring to those locations.

Do people have advice on what whether mounting at the top of the cab would be too high? Although the truck would be road legal in Europe, I am not worried about legal height for the road.

Should I put on floods or spots?

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Do you ever plow while it is still snowing? If you do, and it is dark enough that you need your lights, then you will HATE having them up at the cab. The light reflects off the snow that is in the air and comes right back in your face. If I were you, I would mount a pair on top of the hood as close to the front of the truck as possible. Basically, try to mimic the headlight positioning of a normal snow plow that you would see on a pickup. Then, if you want to have a second set on a separate switch mounted up high on the cab to use when it isn't snowing for extra light, then you can mount those where you were talking about. I would NOT have my only set of lights up there. And again, if you did mount lights up there, I would switch them separately from the others so you can leave them off when it is still snowing.

Do you ever plow while it is still snowing? If you do, and it is dark enough that you need your lights, then you will HATE having them up at the cab. The light reflects off the snow that is in the air and comes right back in your face. If I were you, I would mount a pair on top of the hood as close to the front of the truck as possible. Basically, try to mimic the headlight positioning of a normal snow plow that you would see on a pickup. Then, if you want to have a second set on a separate switch mounted up high on the cab to use when it isn't snowing for extra light, then you can mount those where you were talking about. I would NOT have my only set of lights up there. And again, if you did mount lights up there, I would switch them separately from the others so you can leave them off when it is still snowing.

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I haven't yet with the truck. I have with the forklift, before I got the plow put on my truck. Fortunately the buildings have downlights every 42 feet, so it wasn't too bad.

If I put them over the moldboard they are still more than 5' up. I had figured that I would try and get them as far away as possible from eye level, either up or down, and I have seen loaders/skidsteers with lights high.

It sounds like up is a bad idea, and just over the moldboard would be better.

I haven't yet with the truck. I have with the forklift, before I got the plow put on my truck. Fortunately the buildings have downlights every 42 feet, so it wasn't too bad.

If I put them over the moldboard they are still more than 5' up. I had figured that I would try and get them as far away as possible from eye level, either up or down, and I have seen loaders/skidsteers with lights high.

It sounds like up is a bad idea, and just over the moldboard would be better.

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It isn't so much HOW HIGH they are as it is WHERE they are in relation to you and the windshield. When I plowed with a 3/4 ton p/u, I had a strobe mounted on a threaded mast that was centered in the bed (side to side) and up against the front of the bed, so the post was centered in my back window and out about 4". One day, I got the bright idea to mount a work light that hung down off the bottom of my warning beacon just outside the rear glass. I had a switch in the cab so I could have it on whenever I wanted, thinking that I would use it while loading my tailgate spreader, but also would give good light for backing up. First storm I went out in and started plowing, I turned the light on thinking "this is going to be great." Yeah, it was.......a great big pain in the a$$. The light reflected off the snow just outside the window and back into the cab and into my face. It was blinding and I hated it. Needless to say, it came off the next day and I mounted it onto the tailgate spreader, that way it could be used for backing up and for checking my spreader pattern. That worked great and I just got to where I would drive over to where one of the parking lot lights was and park under that when I loaded the spreader.

Moral of the story is, I think even if they are at eye level, as long as they are way out front and not right up at the windshield, you will have better luck. JMO

Your eyes will pick up the first thing it reflects off best first. If it's a panel of the truck ,the hood, the back of the plow etc it will limit what you see past that point. It has less to do with the light and more to do with how your eyes focus at night. Perfect example is trying to look past a campfire at night....

I needed to limit the speed of the plow moving, given the size of the hydraulic pump, in case someone had the engine revved up when they went to move it.

I developed the schematic shown in the photo. The pressure side is the rod side in my installation.

In order to limit the lifting rate, I found some hydraulic flow regulators that limit flow to 9 gpm independent of the inlet pressure in one direction. They were still in the original Lockheed mid 1950s packaging, so probably off of a PV-2 or something. Those go on to limit the lifting, and are free-flowing in the other direction. Unlike the commercial airlines, the military never moved away from mineral-based hydraulic fluid so I won't have a seal compatibility issue.

To limit the drop speed, I have needle valves. They are free-flowing when the plow is being lifted, but restrict the flow coming out of the rod side when the plow is being powered down or floating down. The needle valve has a set screw to lock it.